-- Test of Aerojet's AJ26 Engine Verifies Performance Capabilities of Liquid Propulsion System for Company's New Medium-Class Space Launch Vehicle --
-- Critical Test Clears the Way for Continued Development of First Flight Vehicle and Subsequent Engine Acceptance Testing at Stennis Space Center in Mississippi --

DULLES, Va., Nov 11, 2010 (BUSINESS WIRE) --

Orbital Sciences Corporation (NYSE: ORB), one of the world's leading space technology companies, today announced the successful test firing of the liquid fuel AJ26 engine that will power the first stage of the company's Taurus(R) II space launch vehicle. In a test conducted yesterday at NASA's Stennis Space Center in Mississippi, Orbital and its engine supplier Aerojet, a unit of GenCorp (NYSE: GY), test fired an AJ26 engine at the E-1 test stand. The E-1 test stand was refurbished by Stennis over the past year specifically for Orbital's Taurus II program. The AJ26 test firings at Stennis are being conducted to verify the upgrades made by Orbital and Aerojet to the baseline NK-33 engine and overall engine performance in its final flight configuration.

This initial test, the first in a series of three firings, lasted 10 seconds and served as a short-duration readiness firing to verify AJ26 engine start and shutdown sequences, E-1 test stand operation, and ground test engine controls. Preliminary data review indicated that all test objectives were met. The test was conducted using a joint operations team comprised of Orbital, Aerojet and Stennis engineers, with Stennis personnel acting in the role of test conductor. The joint operations team, in conjunction with other NASA engineers, will conduct an in-depth data review of all subsystems in preparation for the upcoming 50-second hot-fire acceptance test to be performed in several weeks. A third hot-fire test at Stennis is also planned for the first engine to verify tuning of engine control valves.

The E-1 stand used for the test is located in the E complex at the Stennis Space Center and was modified by Stennis over the past year to accommodate the Taurus II program's AJ26 first-stage engine. Modifications included conversion from horizontal test orientation to vertical orientation through construction of a below-grade flame duct and the addition of subcooled liquid oxygen supply capability. Each engine pulled from Aerojet's stock in Sacramento, CA, and subsequently modified to the AJ26 configuration, will be acceptance tested at Stennis prior to being shipped to the Taurus II integration site at Wallops Flight Facility, VA.

About the AJ26 Rocket Engine

The AJ26 is a commercial derivative of the NK-33 engine that was first developed for the Russian rocket that would have taken cosmonauts to the moon. As the world's first oxidizer-rich, staged-combustion, oxygen/kerosene rocket engine, it achieves very high performance in a lightweight, compact package. Aerojet has been developing design modifications to make the engine suitable for commercial launchers since the mid-1990's. Since its original development, more than 200 NK-33 engines were built and 575 engine tests conducted, totaling more than 100,000 seconds of test time.

About the Taurus II Launch Vehicle

Orbital is developing the Taurus II medium-class space launch vehicle to boost payloads into a variety of low Earth and geosynchronous transfer orbits and to Earth escape trajectories. Taurus II incorporates proven technologies from the company's Pegasus(R), Taurus(R) and Minotaur rockets, and is supported by a "best-in-class" network of suppliers from the U.S. and around the world.

The Taurus II program currently has a backlog of nine launches, beginning with the Commercial Orbital Transportation Services (COTS) project, a joint research and development effort with NASA to develop a system capable of safely and reliably supplying the International Space Station (ISS) with essential cargo. Orbital is also under contract with NASA for the Commercial Resupply Services (CRS) program with an eight-mission, $1.9 billion agreement to deliver cargo to the ISS from 2011 through 2015.

In addition to its work with NASA on the COTS and CRS programs, Orbital is also offering the Taurus II rocket to U.S. civil government, military and commercial customers for dedicated launch services for medium-class satellites. From its Wallops Island, Virginia launch site, Taurus II will be capable of supporting mid-inclination and polar orbiting spacecraft weighing approximately 10,500 lbs. and 5,500 lbs., respectively. Development of a West Coast launch capability is planned for the future to optimize performance to high-inclination orbits.

About Orbital

Orbital develops and manufactures small- and medium-class rockets and space systems for commercial, military and civil government customers. The company's primary products are satellites and launch vehicles, including low-Earth orbit, geosynchronous-Earth orbit and planetary exploration spacecraft for communications, remote sensing, scientific and defense missions; human-rated space systems for Earth-orbit, lunar and other missions; ground- and air-launched rockets that deliver satellites into orbit; and missile defense systems that are used as interceptor and target vehicles. Orbital also provides satellite subsystems and space-related technical services to U.S. Government agencies and laboratories. More information about Orbital can be found at http://www.orbital.com

Note to Editors: High-resolution photos and a video of the test firing are available on Orbital's web site at: http://www.orbital.com/TaurusII/

Photos/Multimedia Gallery Available: http://www.businesswire.com/cgi-bin/mmg.cgi?eid=6508252&lang=en

SOURCE: Orbital Sciences Corporation

Orbital Sciences Corporation
Barron Beneski, 703-406-5528
Public and Investor Relations